openzeppelin-contracts/contracts/token/ERC721/README.adoc

= ERC 721

[.readme-notice]
NOTE: This document is better viewed at https://docs.openzeppelin.com/contracts/api/token/erc721

This set of interfaces, contracts, and utilities are all related to the https://eips.ethereum.org/EIPS/eip-721[ERC721 Non-Fungible Token Standard].

TIP: For a walk through on how to create an ERC721 token read our xref:ROOT:erc721.adoc[ERC721 guide].

The EIP consists of three interfaces, found here as {IERC721}, {IERC721Metadata}, and {IERC721Enumerable}. Only the first one is required in a contract to be ERC721 compliant. The core interface and the metadata extension are both implemented in {ERC721}. The enumerable extension is provided separately in {ERC721Enumerable}.

Additionally, {IERC721Receiver} can be used to prevent tokens from becoming forever locked in contracts. Imagine sending an in-game item to an exchange address that can't send it back!. When using <<IERC721-safeTransferFrom,`safeTransferFrom`>>, the token contract checks to see that the receiver is an {IERC721Receiver}, which implies that it knows how to handle {ERC721} tokens. If you're writing a contract that needs to receive {ERC721} tokens, you'll want to include this interface.

Additionally there are multiple custom extensions, including:

* designation of addresses that can pause token transfers for all users ({ERC721Pausable}).
* destruction of own tokens ({ERC721Burnable}).

NOTE: This core set of contracts is designed to be unopinionated, allowing developers to access the internal functions in ERC721 (such as <<ERC721-_mint-address-uint256-,`_mint`>>) and expose them as external functions in the way they prefer. On the other hand, xref:ROOT:erc721.adoc#Presets[ERC721 Presets] (such as {ERC721PresetMinterPauserAutoId}) are designed using opinionated patterns to provide developers with ready to use, deployable contracts.


== Core

{{IERC721}}

{{IERC721Metadata}}

{{IERC721Enumerable}}

{{ERC721}}

{{ERC721Enumerable}}

{{IERC721Receiver}}

== Extensions

{{ERC721Pausable}}

{{ERC721Burnable}}

== Presets

These contracts are preconfigured combinations of the above features. They can be used through inheritance or as models to copy and paste their source code.

{{ERC721PresetMinterPauserAutoId}}

== Utilities

{{ERC721Holder}}